Quantum corrections to the path integral of near extremal de Sitter black holes

A bstract We study quantum corrections to the Euclidean path integral of charged and static four-dimensional de Sitter (dS 4 ) black holes near extremality. These black holes admit three different extremal limits (Cold, Nariai and Ultracold) which exhibit AdS 2 × S 2 , dS 2 × S 2 and Mink 2 × S 2 near horizon geometries, respectively. The one-loop correction to the gravitational path integral in the near horizon geometry is plagued by infrared divergencies due to the presence of tensor, vector and gauge zero modes. Inspired by the analysis of black holes in flat space, we regulate these divergences by introducing a small temperature correction in the Cold and Nariai background geometries. In the Cold case, we find a contribution from the gauge modes which is not present in previous work in asymptotically flat spacetimes. Several issues concerning the Nariai case, including the presence of negative norm states and negative eigenvalues, are discussed, together with problems faced when trying to apply this procedure to the Ultracold solution.